Pulse generators such as pacemakers or defibrillators are implanted in the body for electrical cardioversion and/or pacing of the heart. Electrodes, which are used to apply electrical energy, are coupled with the pulse generator and are implanted in or about the heart. The electrodes are used to reverse (i.e., defibrillate or cardiovert) certain life threatening arrhythmias, or to stimulate contraction (pacing) of the heart. Electrodes have also been used to sense near the signal node in the atrium of the heart and to deliver pacing pulses to the atrium.
A pulse generator is implanted during a surgical procedure under the skin of an individual. One desirable characteristic of such a device is that it has a relatively small volume or size. This is to increase the comfort to the patient, to prevent protrusion of the device from beneath the skin, and to prevent interference of the device with adjacent vital organs of the individual. One way to reduce the size of the pulse generator is to utilize small electronic components within the device, and to place the small electronic components closer together on the substrate. In addition, integrated circuit chip carriers are used to attach integrated circuits to circuit boards. The chip carriers allow for high density and complex interconnections between the integrated circuit and the circuit board.
When electronic components are placed closer together and/or complex interconnections are implemented, sensitive electronic circuitry and components are susceptible to electromagnetic interference (EMI) emanating from other circuits and components. One way to address the problem of EMI is to incorporate EMI shields to isolate the sensitive circuits from other circuits. The EMI shields are in the form of a separate piece of conductive tape or foil which is incorporated into the implantable device. The physical size of the foil limits efforts to reduce the overall size of the device, since the separate component consumes valuable space and volume within the implantable device.
In addition, electrical connections between the small electronic components must be made. Electrically conductive conduits are used to make electrical and mechanical connections between various circuits and discrete components in implantable defibrillators and pacemakers. One example of making such connections is metalized high temperature ceramic (HTCC) or metalized low temperature ceramic (LTCC). However, LTCC and HTCC technologies require screen printing specific traces on numerous specific ceramic layers followed by a high pressure lamination and elevated temperature (e.g. 850 degrees Celsius) to create a substrate of alternative conductors and insulators, which can be harmful to temperature sensitive components. Alternatively, printed circuit boards are another option. However, the printed circuit boards typically use etched copper foil which is laminated to a rigid organic fiber board in a multi layer arrangement using a variety of adhesive permanently binding the multi-layers together.
Accordingly, there is a need for reducing the overall size of the implantable device. There is also a need for an implantable medical device which simplifies the interconnect routing between the various electronic components of the device. Furthermore, there is a need to reduce EMI of the implantable medical device.